We often hear about the so-called retirement crisis, and most seniors kick off their golden years with their IRAs or 401(k)s grossly underfunded. But once in a while, some good news emerges on the retirement front, and this time, it's the fact that one in six retired Americans is actually a millionaire, according to data from financial planner United Income. Furthermore, the average level of wealth among retirees is a rather impressive $752,000, which is certainly something to be happy about.

But not so fast. The problem with that $752,000 average is that it's easy enough for a small cluster of uber-wealthy individuals to skew that number in an upward direction. But when we look at the median wealth among retirees, it's just over $200,000. And when you have a median that's considerably lower than the average, it means that far more seniors have less than $752,000 at their disposal than those who have more.

Man counting 100-dollar bills

Image source: Getty Images.

Now, if you still have plenty of time in the workforce ahead of you, you don't need to panic if your savings level is hovering around the $200,000 mark, or even well below it. But the older you are, the more a lackluster savings balance becomes a concern. If you're in the latter situation, here are a few steps you can take to build more wealth for retirement.

1. Take advantage of catch-up contributions

One benefit of being older is having an even greater opportunity to fund your nest egg. Currently, workers under 50 can sock away up to $5,500 a year in an IRA, and $18,500 in a 401(k). If you're 50 or older, however, these limits increase to $6,500 and $24,500, respectively. Therefore, if you're behind on savings, taking advantage of catch-up contributions is a good way to get on track.

What sort of a difference might that make? Let's assume you're saving in a 401(k), are currently sitting on a $100,000 balance, and have another 10 years in the workforce before reaching full retirement age for Social Security purposes. If you were to save $18,500 a year for the next decade, you'd wind up with a total of $452,000, assuming your investments generate an average annual 7% return. But if you were to max out that 401(k) instead, you'd be sitting on $535,000. And that extra $83,000 will no doubt go a long way in retirement.

2. Bank your raises

Whether you get merit-based raises or cost-of-living raises, socking away any extra cash you get for the remainder of your career will help you accumulate more wealth in your retirement plan. And it pays to bank your raises automatically, because if you do so without ever getting that cash in your paychecks, you won't actually come to miss it.

3. Invest aggressively

Even if you're older, it still pays to load up on stocks in your IRA or 401(k). Though stocks are more volatile than bonds, they've historically delivered much higher returns. And as long as you have about a 10-year savings window or longer, you should have no problem letting them occupy a sizable chunk of your portfolio.

In the above example, we saw that maxing out a 401(k) for 10 years at a 7% average annual return would bring a $100,000 balance up to $535,000. Well, that 7% is actually a reasonable assumption for a stock-heavy portfolio. But if you were to stick with safer investments, like bonds, and generate just a 3% average annual return instead, your ending balance would be just $415,000.

4. Get a side hustle

Maxing out a retirement plan -- especially a 401(k) -- is easier said than done. But if you're looking to boost your wealth for your retirement, and you're struggling to part with such a large chunk of your paycheck, you might consider getting a side hustle instead. In fact, of the millions of working Americans who have a second job, 14% do so for the express purpose of funding a retirement plan. Furthermore, working a side gig later in life will buy you the option to take that job with you into retirement, thereby securing an additional income stream should you come to need it.

Though the average wealth level among retirees is rather substantial, there are plenty of seniors who continue to struggle financially. If you'd rather not be one of them, make a point of boosting your nest egg while you can.